Conventional microelectronic devices often have vertical electrical connections that extend through wafers or semiconductor dies. One type of vertical electrical connection is a through-silicon via (“TSV”) often used in stacked semiconductor devices. A TSV in the wafer can be electrically coupled to a bond pad. A pillar can electrically couple the bond pad to another device, such as an active side of a semiconductor die. Before forming the pillar, wafer-level probing is often used to evaluate electrical characteristics of the wafer and involves contacting bond pads with probe pins to send electrical signals to the wafer. Unfortunately, the probe pins may damage (e.g., roughen, scratch, gouge, etc.) the bond pads. If a bond pad is made of aluminum, a probe pin can pass through a thin oxide layer on the bond pad and cause significant damage to the bond pad. Such damage is commonly referred to as a “probe mark” and may impact subsequent processing and decrease product yields.
FIGS. 1 and 2 show a portion of a bond pad assembly 90 of a conventional wafer 100. Referring to FIG. 1, the wafer 100 includes a polyimide layer 110 having an opening 120 at a central region of a probed bond pad 130 (illustrated in phantom) of the bond pad assembly 90. A probe mark in the form of an elongated groove 140 extends across an exposed surface 142 (FIG. 2) of the bond pad 130 and underneath the polyimide layer 110. The polyimide layer 110 is deposited and the openings 120 are formed by aligning and development after wafer-level probing. FIG. 2 shows unwanted residual material 144 (e.g., polyimide material at the bottom of the opening 120) left due to improper development of the polyimide layer 110. Such residual material 144 is often referred to as “scumming,” and excess scumming may make it difficult to form a pillar (not shown) that contacts the bond pad 130.
FIG. 3 shows a stage of forming the opening 120 in the polyimide layer. Light rays or other radiation, represented by arrows, is used to develop the polyimide layer 110. The elongated groove 140 causes scattering of the radiation. For example, rays reflected from ends 143, 145 of the elongated groove 140 can travel towards the center of the opening 120 and cause crosslinking of the polyimide which results in insufficient development of the polyimide material. This can cause scumming in the form of a residual feature 150 to be left in the opening 120. The scattered radiation can also lead to improperly shaped openings (e.g., irregular shaped openings).
FIG. 4 shows an interface between a pillar 160 and a conventional probed bond pad 162. In this example, a probe mark 164 can result in a poor connection (e.g., an electrical connection, a mechanical connection, etc.) between the pillar 160 and the bond pad 162. The probe mark 164 may also have rough and irregular surfaces that prevent the formation of a uniform barrier/seed layer on the bond pad 162. When this occurs, a processing substance (e.g., an etchant, an etching solution, etc.) can pass through openings in the barrier/seed layer and corrode the underlying bond pad 162. If the bond pad 162 is made of aluminum, the upper surface of the bond pad 162 can experience significant corrosion and result in a poor electrical connection and decrease product yields.